Sound-reproducing diaphragm and process of making the same.



'1. A. S TEURER. SOUND REPRODUCING DIAPHRAGM AND PROCESS OF MAKING THE SAME.

APPLICATION FILED DEC-17,1917- Patented Apr. 30, 1918.

R O T N E V m 4 ATTONEM UNITED STATES PATENT OFFICE,

JOHN A. STEURER, OF NEW YORK, 11'. Y.

SOUND-REPRODUCING DIAPHRAGM AND PROCESS OF MAKING THE SAME.

Specification of Letters IPatent. Patnted Apl'. 30, 1918.

Application filed December 17,1917. Serial No. 207,446.

To all whom it may concern:

Be it known that I, JOHN A. Srnonan, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Sound-Reproducing Diaphragms and Processes of Makingthe Same; and I do hereby declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention consists in the novel fea tures hereinafter described, reference being had to the accompanying drawing which illustrates one embodiment of the invention selected by me for purposes of illustration, and the said invention is fully disclosed in the following description and claims:

In my former Patent, #1,192,833, dated July 25th, 1916, I have described and claimed a clarifying disk composed of a phenolic condensation product having embodied therein strata of fibrous material parallel with the diaphragm, adhesively secured to the central portion of the diaphragm for the purpose of eliminating metallic resonance and clarifying the tone produced by the diaphragm. The material which I have referably used for these clarifying disks is bakelite dilecto, and the results obtained have been eminently satisfactory, so far as the tone was concerned. I have experienced, however, some difiiculty with the use of this type of diaphragm on account of the fact that if the cementing of the disk is not most carefully done, they in some instances tend I to cleave .away from the diaphragm. One of the objects of my present inventlon 1s to form a clarifying disk for the same purpose as above set forth, which shall be an integralpart of the diaphra itself, and which therefore cannot possibly be affected in its use. In carr ing out my invention, I take a sheet of t in, porous material, such as wood, veneer, blotting paper, on other mate rial, as a base, and impregnate it with a solution material which in its final state will become hard, tough and elastic, without becoming brittle. I then treat a central, circular portion of the diaphragm so as toimpregnate it more thoroughly than the surrounding portions, thereby increasing the density of the central circular ortion and forming a sound clarifying di as an integral part of the diaphragm itself. I prefer to use as a base a sheet of material of fibrous character in which the fibers are in what may be termed a felted condition, and the material which I-prefer to use is blotting paper. In carrying out my improved process, according to one form thereof for example, I saturate a single thickness of blotting paper with a thin solution of a phenolic condensation product, such as bakelite or condensite, dissolved in'a suitable vehicle, and dry the same. The individual diaphragms maybe formed either before or after the treatment of the blotting paper with the phenolic condensation product. I then treat a circular central portion, of any desired diameter, of the diaphragm with a greater amount of the solution ofv said condensation product, which in this instance may' be either in the same or a thicker solution, and permit the central portion to dry. The central portion will therefore have taken up a much larger quantity of the condensation product than the surrounding portions and will be consequently much more dense. The diaphragm is now. baked for such a time and at such a temperature as will convert the phenolic condensation product into a hard, tough, elastic condition, without being brittle. I have found that a temperature of substantially 200 Fahrenheit is best adapted for producing this condition.

A diaphragm formed as herein described thus comprises a single flat sheet of uniform thickness and composed of the same materials throughout, while having the central circular portion of greater density, forming an integral sound clarifying disk in which there is a greater proportion of the elastic, hard and tough material.

In the accompanying drawing,

Figure 1 represents a plan view of my improved diaphragm and Fig. 2 represents a sectional liew of the same.

In" these figures, 1 represents the outer portion of the diaphragm and ,2 represents tion of sound it gives forth a clear and sweet tone, free from metallic resonance, which I attribute to the combined action of the fibrous material and the hard, tough, elastic material with which it is impregnated, the qualities of each of which are united in the resulting tones.

While I prefer to form these diaphragms, as herein described, with a central portion of greater density, forming the sound clarifying disk as an integral part of the diaphragm itself, Without increasing the thickness of the diaphragm, I have also obtained excellent results by the use of diaphragms formed of a porous base such as blotting paper, impregnated With a solution of a phenolic condensation product and baked to convert the latter into a hard, tough and elastic condition Without increasing the den sity of the circular portion, and I claim the same as my invention.

While I'prefer to employ as the impregnating material a solution of a phenolic condensation product, I may also employ any other substance as the impregnating material, Which in this final state Will become hard, tough and elastic and obtain the results desired, for example, certain gums dissolved in a suitable vehicle and applied to the absorbent material and dried with or without heat, may be employed, the central circular portion being impregnated to a greater extent so as to form the integral sound clarifying disk. While ll prefer to impregnate all portions of the film With the same material, I may in some instances impregnate the outer or marginal portions of the diaphragm with a solution of one material, as for example, a solution-of the resinous gum, and impregnate the central circular portion to a greater extent with a solution of a phenolic condensation product, and these modifications are Within the scope of my invention.

What I claim and desire to secure by Letters Patent is:

l. A sound reproducing diaphragm consisting of a fiat sheet of material and having a central, concentric, circular portion of greater density than surrounding portions, forming a sound clarifying disk.

2. A sound reproducing diaphragm comprising a fiat sheet of absorbent material impregnated with a hard, tough and elastic material throughout and having a central, circular portion more densely impregnated than the surrounding portions to form an integral sound clarifying disk.

3. A sound reproducing diaphragm consisting of a single sheet of absorbent material impregnated With a phenolic condensation product throughout, in a hard, tough and elastic condition.

4. A sound re reducing diaphragm consisting of a sing e sheet of absorbent material impregnated with a phenolic condensation product throughout, in a hard, tough and elastic condition, and having a circular central portion more densely impregnated with said condensation product than the surrounding portions, forming an integral sound clarifying disk.

5. A sound reproducing diaphragm consisting of a single sheet of absorbent material having its fibers in loosely felted condition, impregnated with a phenolic condensation product in a hard, tough and elastic condition.

6. A sound reproducing diaphragm consisting of a single sheet of absorbent material having its fibers in loosely felted condition, impregnated With a phenolic condensation product in a hard, tough and elastic condition, and havin a central, circular portion more densely lmpregnated With said condensation product than the surrounding portions to form an integral sound clarifying disk.

A sound reproducing diaphragm .consisting of a disk of blotting paper impregnated with a phenolic condensation product in a hard, tough and elastic condition.

8. A sound reproducing diaphragm consisting of a disk of blotting paper impreg nated With a phenolic condensation product in a hard, tough and elastic condition, and having a central, circular portion impregnated more densely with said condensation product than the surrounding portions, and

forming an integral sound clarifying disk.

9, The herein-described process of producing a sound reproducing diaphragm which consists in impregnating a single sheet of absorbent material With a thin solution or a phenolic condensation product and drying the same, then further impregnating a circular, central portion of the diaphragm with said condensation product and then baking the diaphragm'to convert the said conden-.

sation product into a hard, tough and elastic condition and thereby form in the center of fil al/{diaphragm an integral sound clarifying 10. The herein-described process of producing a sound reproducing diaphragm which consists in impregnating a single sheet of absorbent material With a solution of a resinous material, and impregnating a circular, central portion of the diaphragm to a greater extent than the surrounding portions with a solution of resinous material to increase the density of said central portion beyond that of the surrounding portions and form an integral sound clarifying disk.

ln testimony whereof I aifix my signature.

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